The purpose of the proposed research is to develop a neuropsychological perspective on psychiatric disorders. The method is to obtain clinical, behavioral and neuropsychological data pertinent to regional brain function in psychiatric patients. These data are compared to findings in neurological patients with unilateral stroke and parkinson disease and in normal controls. Clinical data will be derived from standardized neurological and psychiatric examinations. Behavorial data will be obtained with a comprehensive neuropsychological battery which measures sensory-perceptive, motor, cognitive, emotional and conative functions. Regional brain activity will be determined by the 133-Xenon inhalation technique for measuring regional cerebral blood flow (rCBF). The rCBF measurements will be performed during rest and during activation with cognitive and emotional tasks. In order to confirm the relationship between the behavioral and physiological abnormalities and the clinical status, all measures will be obtained in a group of patients during the acute phase of illness and again after they are stable (3-5 months follow up). The investigation will examine receptive and expressive functions along the following behavioral dimensions: 1. Cognitive; verbal contrasted with spatial. 2. Emotional; euphoria is contrasted with dysphoria. These behavioral dimensions will be mapped into the following regional dimensions: 1. Laterality; left compared to right hemisphere. 2. Anterior-posterior; frontal, temporal and parietal lobes. The functional mapping will be done in twelve experiments. These experiments will be carried out in three populations: 1. Schizophrenics 2. Depressives 3. Matched controls. The experiments will systematically vary stimulus modality and task.